Research On Mechanical Properties Of Doubler Plate Reinforced Tubular T-Joints

This paper focus on the experiments on static behavior of a tubular T-joint and two doubler plate reinforced tubular T-joints (DP-T-joints) under the axial tensile load on brace. The strengthen effect of doubler plate reinforced tubular T-joints (DP-T-joints) under bending moment, and a parametric study is then conducted to understand the influence of the geometric parameters on the DP-T-joints. The design of test specimens、the loading scheme and the testing steps are introduced, methods to estimate the ultimate bearing capacity of the four joints are proposed, the phenomena and the main results of tests are obtained. At the same time, the strengthen effect of doubler plate reinforced tubular T-joints (DP-T-joints) under bending moment are obtained.Experimental results showed that the failure mode of specimen JD-A were plastic fracture at the connecting face of chord, the DP-T-joints specimen JD-B and JD-C were weld failures at the intersectional parts of brace and chord. DP-T-joints specimens are unable to resists load. According to data collected in experiments,we can know that:the principle of doubler plate reinforced is by means of the thickness effect and force transmission effect of plate. The load of brace spread to the chord surface. Between the brace and chord, A new plate have been set. Changing the load transmission path and the performance of the force of chord, And then improving the performance of the tubular T-joints. The ultimate tensile carrying capacity of doubler plate reinforced tubular T-joints (DP-T-joints) is one point five-fold higher, So between the brace and chord, A new plate have been set can effectively improve the tubular T-joints ultimate tension capacity. The strengthen effect of two different doubler plate is the same. From making simple angle to consider the plate of a=90°is good, From the project cost saving the plate of α=45°is good. The analysis of equivalent stress distribution curve of the three tubular T-joint tests of intersecting area of the brace and chord, In the elastic phase, the stress distribution of three tubular T-joints are very complicated. The phenomenon of stress concentration of the test one is more apparent the test two and test three. So between the brace and chord, We have set a new plate can effectively improve stress concentration of the tubular T-joints. The finite-element analysis of the results and the test results are in good agreement, and to verify the accuracy of the test.According to the finite-element analysis on bending capacity of the tubular T-joint, we can know that:Between chord and brace, using doubler plate can increase the ultimate bending strength and improve the stress concention property. The length parameter and the width parameter of the doubler plate does not have significant effect on the bending strength of the joint. For the width parameter, u=90°is the best result. The parameter of the doubler plate thickness has clearly effect on the ultimate bending strength of the reinforced joints.But the ultimate bending strength of the reinforced joints not always increase with the doubler plate thickness.when the doubler plate thickness is too thick, the ultimate bending capacity of tubular T-joint by_brace_failure to decide.So the doubler plate thickness is too thick is unfavorable to the structure.